A variety of substances have heretofore been proposed for use being added to thermoplastic resins to impart the molded articles thereof with deodorizing function or antibacterial function or with both of these functions.
As for the deodorizing function, it has been known that a wide range of smelling components can be deodorized by using, for example, inorganic fillers such as activated carbon, porous zeolite or sepiolite, or by using a titanium oxide to which photo-catalytic action is applied (patent document 1). The deodorizing method that uses the inorganic filler, however, is based on the adsorption and removal of bad-smelling components by the porous substance, and no longer maintains its effect if the amount of adsorption exceeds a predetermined level. The titanium oxide which oxides and decomposes bad-smelling components by the photo-catalytic action, requires a source of light, and works to oxidize and degrade not only the bad-smelling components but also the carrier that is in contact with the catalyst, arousing a problem in that a special technical countermeasure is necessary. There has, further, been proposed a deodorant using ultrafine particles of a metal, i.e., a deodorant containing a colloidal solution of ultrafine metal particles obtained by reducing a metal ion-containing solution as an effective component (patent document 2). It has been known that the colloid of ultrafine metal particles has a high deodorizing property as well as antibacterial property. Due to its very strong aggregating property, however, it is very difficult to store the above deodorant for extended periods of time in a stable state, or to stably disperse the deodorant in the matrixes of the thermoplastic resins or of the coating material components while preventing the particle thereof from being aggregated together.
On the other hand, in an attempt to produce a resin composition containing ultrafine metal particles having a narrow particle size distribution which are stably dispersed therein and to produce molded articles thereof by a very simple and widely employed method, the present inventors have proposed a method of forming ultrafine metal particles in a molded resin article by heating and molding a mixture of an organic compound of a metal and a resin at a temperature not lower than a temperature at which the organic compound of a metal starts thermally decomposing but lower than a temperature at which the resin deteriorates (patent document 3). The present inventors have also clarified that the resin composition that uses the ultrafine metal particles as an effective component for producing deodorizing function and antibacterial function, excels in deodorizing bad-smelling components such as methyl mercaptan and the like and in exhibiting antibacterial property against colon bacillus etc. (patent documents 4 and 5).